エラーチェック

internal/cli/cli.go

@@ -48,6 +48,16 @@ func run(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
 		return 0
 	}
 
+	// webhook URL の解決: flag > env
+	webhookURL := strings.TrimSpace(opt.WebhookURL)
+	if webhookURL == "" {
+		webhookURL = strings.TrimSpace(os.Getenv("SLACK_WEBHOOK_URL"))
+	}
+	if webhookURL == "" {
+		fmt.Fprintln(stderr, "Slack webhook URL is required. Set --webhook or SLACK_WEBHOOK_URL.")
+		return 2
+	}
+
 	msg, err := message(fs.Args(), stdin)
 	if err != nil {
 		fmt.Fprintln(stderr, "read message error:", err)